Day 18 Notebook

#input<-read_lines("Day18Sample.txt")
input<-read_lines("../../AoCData/AOC2018/Day18.txt")
### Matrix
landscape<-matrix(0,nrow=length(input)+2,ncol=nchar(input[1])+2)

lsc<-lapply(input,function(x){
x<-unlist(str_split(x,""))
x[which(x==".")]<-"0"
x[which(x=="|")]<-"1"
x[which(x=="#")]<-"10"
x<-as.numeric(x)})

for(i in 1:length(lsc)){landscape[i+1,]<-c(0,unlist(lsc[[i]]),0)}

Part 1

forestgrow<-function(lsc,reps){
  r<-1
  while(r<=reps){
    nextforest<-matrix(NA,ncol=ncol(lsc),nrow=nrow(lsc))
    nextforest[1,]<-0
    nextforest[nrow(nextforest),]<-0
    nextforest[,1]<-0
    nextforest[,ncol(nextforest)]<-0
    for(i in 2:(nrow(lsc)-1)){
      for(j in 2:(ncol(lsc)-1)){
        nine<-sum(lsc[(i-1):(i+1),(j-1):(j+1)])
        switch(as.character(lsc[i,j]),
               "0"={if(nine%%10>=3){nextforest[i,j]<-1}else{nextforest[i,j]<-0}},
               "1"={if(nine>30){nextforest[i,j]<-10}else{nextforest[i,j]<-1}},
               "10"={if(nine%%10>=1&nine>=20){nextforest[i,j]<-10}else{nextforest[i,j]<-0}},
               cat("something is wrong\n"))
                #cat(i,j,lsc[i,j], nine,nextforest[i,j],"\n")
                }}
    lsc<-nextforest
    r<-r+1}
  trees<-length(which(lsc==1))
  lumberyards<-length(which(lsc==10))
  resources<-trees*lumberyards
  list(trees,lumberyards,resources,lsc)}

p1<-forestgrow(landscape,10)
part1<-p1[[3]]
part1

[1] 678529

Part 2

Depends heavily on the data, the real data has the pattern below Start by graphing to see if there’s a pattern for something that looks like a pattern -

forestgrowanimation<-function(lsc,reps){
  r<-1
  anim<-as.data.frame(matrix(ncol=4,nrow=0))
  cel<-melt(lsc)
  cel<-cbind(cel,rep(0,nrow(cel)))
  names(cel)<-c("y","x","resources","minutes")
  anim<-rbind(anim,cel)
  names(cel)<-c("y","x","resources","minutes")

  while(r<=reps){
    nextforest<-matrix(NA,ncol=ncol(lsc),nrow=nrow(lsc))
    nextforest[1,]<-0
    nextforest[nrow(nextforest),]<-0
    nextforest[,1]<-0
    nextforest[,ncol(nextforest)]<-0
    for(i in 2:(nrow(lsc)-1)){
      for(j in 2:(ncol(lsc)-1)){
        nine<-sum(lsc[(i-1):(i+1),(j-1):(j+1)])
        switch(as.character(lsc[i,j]),
               "0"={if(nine%%10>=3){nextforest[i,j]<-1}else{nextforest[i,j]<-0}},
               "1"={if(nine>30){nextforest[i,j]<-10}else{nextforest[i,j]<-1}},
               "10"={if(nine%%10>=1&nine>=20){nextforest[i,j]<-10}else{nextforest[i,j]<-0}},
               cat("something is wrong\n"))
                #cat(i,j,lsc[i,j], nine,nextforest[i,j],"\n")
                }}
    lsc<-nextforest
    
  cel<-melt(lsc)
  cel<-cbind(cel,rep(r,nrow(cel)))
    names(cel)<-c("y","x","resources","minutes")

      anim<-rbind(anim,cel)
    r<-r+1}
  trees<-length(which(lsc==1))
  lumberyards<-length(which(lsc==10))
  resources<-trees*lumberyards
  anim}
mkgraph<-forestgrowanimation(landscape,599)
mkgraph$resources<-as.character(mkgraph$resources)

resourcecolors<-c("0"="#6F4E37","10"="#999999","1"="#00AA00")
lumberfield<-ggplot()+
  scale_fill_manual(values=resourcecolors)+
  geom_tile(data=mkgraph,aes(x=x,y=y,fill=resources))+
  theme(axis.text.x = element_blank(),
        axis.ticks.x = element_blank(),
        axis.text.y = element_blank(),
        axis.ticks.y = element_blank(),
        axis.title.y = element_blank(),
        axis.title.x = element_blank(),
        panel.grid.major = element_blank(),
        panel.grid.minor = element_blank(),
        legend.position="none")+
  scale_y_reverse()+
  coord_fixed()+
  transition_states(minutes,wrap=FALSE)

treegrowth<-animate(lumberfield,nframes=600,renderer = gifski_renderer())
treegrowth

Yes, there’s a pattern

Which looks like it begins repeating after a while - to figure out how often, looking for the minimums -

lowestpoints<-c(FALSE,sapply(2:999,function(x){if(first1000[x]<first1000[x-1]&&first1000[x]<first1000[x+1]){TRUE}else{FALSE}}),FALSE)
first1000[lowestpoints]

It looks like a repeat at 163430

which(first1000==163430)

This shows that the repeat is every 28 - shown again here:

diff(first1000[400:500],28)

So by repeat 500, this is on a 28 minute cycle

Which means that if it goes to 1000000000%%28+560 (560 is high enough and as a multiple of 28 will be basically a “reset”)

1000000000%%28+560

p2<-forestgrow(landscape,(1000000000%%28+560))
part2<-p2[[3]]
part2